The fibroblast growth factor family has emerged as a large family of growth factors involved in soft-tissue growth and regeneration. It presently includes several members that share a varying degree of homology at the protein level, and that, with one exception, appear to have a similar broad mitogenic spectrum, i.e., they promote the proliferation of a variety of cells of mesodermal and neuroectodermal origin and/or promote angiogenesis.
The pattern of expression of the different members of the family is very different, ranging from extremely restricted expressions of some stages of development, to rather ubiquitous expression in a variety of tissues and organs. All the members appear to bind heparin and heparin sulfate proteoglycans and glycosaminoglycans and strongly concentrate in the extracellular matrix. KGF was originally identified as a member of the FGF family by sequence homology or factor purification and cloning. Keratinocyte growth factor (KGF) was isolated as a mitogen for a cultured murine keratinocyte line (Rubin, J. S. et al., Proc. Natl. Acad. Sci. USA 86:802-806 (1989)). Unlike the other members of the FGF family, it has little activity on mesenchyme-derived cells but stimulates the growth of epithelial cells. The Keratinocyte growth factor gene encodes a 194-amino acid polypeptide (Finch, P. W. et al., Science 245:752-755 (1989)). The N-terminal 64 amino acids are unique, but the remainder of the protein has about 30% homology to bFGF. KGF is the most divergent member of the FGF family. The molecule has a hydrophobic signal sequence and is efficiently secreted. Post-translational modifications include cleavage of the signal sequence and N-linked glycosylation at one site, resulting in a protein of 28 kDa. Keratinocyte growth factor is produced by fibroblast derived from skin and fetal lung (Rubin et al. (1989)). The Keratinocyte growth factor mRNA was found to be expressed in adult kidney, colon and ilium, but not in brain or lung (Finch, P. W. et al. Science 245:752-755 (1989)). KGF displays the conserved regions within the FGF protein family. KGF binds to the FGF-2 receptor with high affinity.
Impaired wound healing is a significant source of morbidity and may result in such complications as dehiscence, anastomotic breakdown and, non-healing wounds. In the normal individual, wound healing is achieved uncomplicated. In contrast, impaired healing is associated with several conditions such as diabetes, infection, immunosuppression, obesity and malnutrition (Cruse, P. J. and Foord, R., Arch. Surg. 107:206 (1973); Schrock, T. R. et al., Ann. Surg. 177:513 (1973); Poole, G. U., Jr., Surgery 97:631 (1985); Irvin, G. L. et al., Am. Surg. 51:418 (1985)).
Wound repair is the result of complex interactions and biologic processes. Three phases have been described in normal wound healing: acute inflammatory phase, extracellular matrix and collagen synthesis, and remodeling (Peacock, E. E., Jr., Wound Repair, 2nd edition, W B Saunders, Philadelphia (1984)). The process involves the interaction of keratinocytes, fibroblasts and inflammatory cells at the wound site.
Tissue regeneration appears to be controlled by specific peptide factors which regulate the migration and proliferation of cells involved in the repair process (Barrett, T. B. et al., Proc. Natl. Acad. Sci. USA 81:6772-6774 (1985); Collins, T. et al., Nature 316:748-750 (1985)). Thus, growth factors may be promising therapeutics in the treatment of wounds, burns and other skin disorders (Rifkin, D. B. and Moscatelli, J. Cell. Biol. 109:1-6 (1989); Sporn, M. B. et al., J. Cell. Biol. 105:1039-1045 (1987); Pierce, G. F. et al., J. Cell. Biochem. 45;319-326 (1991)). The sequence of the healing process is initiated during an acute inflammatory phase with the deposition of provisional tissue. This is followed by re-epithelialization, collagen synthesis and deposition, fibroblast proliferation, and neovascularization, all of which ultimately define the remodeling phase (Clark, R. A. F., J. Am. Acad. Dermatol. 13:701 (1985)). These events are influenced by growth factors and cytokines secreted by inflammatory cells or by the cells localized at the edges of the wound (Assoian, R. K. et al., Nature (Lond.) 309:804 (1984); Nemeth, G. G. et al., “Growth Factors and Their Role in Wound and Fracture Healing,” Growth Factors and Other Aspects of Wound Healing in Biological and Clinical Implications, New York (1988), pp. 1-17.
Several polypeptide growth factors have been identified as being involved in wound healing, including keratinocyte growth factor (KGF) (Antioniades, H. et al., Proc. Natl. Acad. Sci. USA 88:565 (1991)), platelet derived growth factor (PDGF)(Antioniades, H. et al., Proc. Natl. Acad. Sci. USA 88:565 (1991); Staiano-Coico, L. et al., Jour. Exp. Med. 178:865-878 (1993)), basic fibroblast growth factor (bFGF) (Golden, M. A. et al., J. Clin. Invest. 87:406 (1991)), acidic fibroblast growth factor (aFGF) (Mellin, T. N. et al., J. Invest. Dermatol. 104:850-855 (1995)), epidermal growth factor (EGF) (Whitby, D. J. and Ferguson, W. J., Dev. Biol. 147:207 (1991)), transforming growth factor-α (TGF-α) (Gartner, M. H. et al., Surg. Forum 42:643 (1991); Todd, R et al., Am. J. Pathol. 138;1307 (1991)), transforming growth factor-β (TGF-β) (Wong, D. T. W. et al., Am. J. Pathol. 143:622 (1987)), neu differentiation factor (rNDF) (Danilenko, D. M. et al., J. Clin. Invest. 95;842-851 (1995)), insulin-like growth factor I (IGF-1), and insulin-like growth factor II (IGF-II) (Cromack, D. T. et al., J. Surg. Res. 42:622 (1987)).
It has been reported that rKGF-1 in the skin stimulates epidermal keratinocytes, keratinocytes within hair follicles and sebaceous glands (Pierce, G. F. et al., J. Exp. Med. 179:831-840 (1994)).